History & examination
Key diagnostic factors
- presence of risk factors (common)
- Key risk factors include acute trauma, history of anterior cruciate ligament injury, history of knee instability or knee malalignment, participation in twisting sports, rough or uneven playing surface, poor ground/weather conditions, and knee joint arthritis.
- knee swelling (common)
- Usually occurs several hours after injury, but is not always present.
- sensation of knee instability or buckling/catching (common)
- Patient often describes sensation of femur and tibia twisting apart from each other (catching or locking) or the knee feeling loose.
- knee pain (common)
- Varies greatly. Some experience minimal pain, while others describe intermittent pain.
- tenderness at joint line and joint line crepitation (common)
- Often due to unstable meniscus tissue and abnormal force transmission.
- positive McMurray's test (common)
- Patient is supine with knee in flexion. Examiner flexes the hip and, with one hand on the joint line, rotates the foot internally and externally. Pain with rotation suggests a meniscal tear. This test has low sensitivity and high specificity for diagnosing a meniscal tear. 
- positive Apley's test (common)
- Patient is prone with knee flexed at 90°. Examiner places axial load on the lower leg while rotating the foot. Patient often feels pain in the affected compartment. 
- positive hyperextension test (common)
- Examiner lifts the heel of the affected leg, hyperextending the knee and adding additional downwards force on the tibia. Patient reports pain in the affected compartment.
- Sensitive but not specific for a torn meniscus.
Other diagnostic factors
- popliteal (Baker's) cyst in chronic cases (common)
- Swelling at the posterior aspect of the knee suggests a popliteal (Baker's) cyst. Popliteal cysts are associated with meniscal pathology in 80% of cases. 
- limited range of motion (common)
- Full flexion and extension may or may not be lacking.
- acute trauma (twisting injury)
- Traumatic meniscal tears most commonly occur in young, active people, usually as a result of trauma sustained during twisting sports such as football and basketball. Skiers, runners, and tennis players are also at risk. Twisting with joint compression puts the soft tissue meniscus at risk of tearing.
- knee joint arthritis
- Degenerative meniscal tear can occur as a result of traumatic and degenerative arthritis.
- knee instability
- Leads to abnormal motions in the knee and abnormal shear stresses, both of which can tear meniscus cartilage.
- hx of anterior cruciate ligament injury
- Leads to knee instability, which in turn leads to abnormal motions in the knee and abnormal shear stresses, both of which can tear meniscus cartilage.
- malalignment of the knee joint
- Places abnormal compression and rotational forces on one side of the joint versus the other, thus increasing the possibility of tearing the meniscus.
- rough or uneven playing surface
- It is suggested that increased friction from various sporting turfs may lead to a meniscal tear.
- poor ground/weather conditions
- Poor conditions with snow, sleet, or rain increase the likelihood of slips, falls, and improper landings, all increasing the risk of a meniscal tear. 
- construction work and manual labour jobs
- These occupations usually involve knee flexion while lifting heavy objects, thereby putting stress on the joint and increasing the risk of meniscal tearing.
- discoid meniscus
- This fails to undergo complete condensation into physiological dimensions and may either lack an attachment to stabilise the posterior horn to the tibia or be discoid in form with normal attachment.
- The incidence of discoid menisci is higher in the Asian population.  Discoid lateral meniscus is found in 3.5% to 5% of meniscal tear patients. 
Last updated: May 20, 2013